Non-contact board inspection probe

ABSTRACT

A board inspection probe for inspecting pattern lines on a circuit board for defects in a non-contact manner. The probe has an electrode for radiating an electrical signal or receiving an electrical signal radiated from a first pattern line. The probe also has a shield to prevent, from reaching the electrode, unwanted radiant waves emitted from pattern lines located in a region except a board region immediately below an electrode surface of the electrode. This shield is terminates near the electrode surface of the electrode, so that radiant waves from only pattern lines located on the board region immediately below the electrode are received.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an inspection probe used forinspecting a board in a non-contact manner, and an inspection method andapparatus using this probe. A target board is represented by a boardprinted with conductive patterns at a small pitch and includes e.g., aflexible board (a “flexible board” includes an LSI package which is notmounted with IC chip and is to be mounted therewith, and will bereferred to simply as a “circuit board” hereinafter). More particularly,the present invention relates to a non-contact board inspection probeand an inspection method and apparatus, all of which are suitable forinspecting local patterns on a board for disconnections and the like.

[0002] The board inspection probe and the inspection method andapparatus of the present invention are effective in inspecting aso-called bare circuit board on which no circuit elements such as ICpackages are mounted yet although conductive patterns having a smallpitch are printed thereon.

[0003] In conventional board inspection, if a board on which conductivepatterns having a small pitch are printed has a large pitch on theelectrode side, as shown in FIG. 1, probes can be brought into contactwith the electrode groups (two or more electrode groups) of the board toenergize the board (power is supplied from one electrode group, and theinspection result is detected on the other electrode group).

[0004] A recent highly-integrated circuit board, however, has smallpitches in not only conductive patterns, but also electrodes. This makesit difficult to accurately bring probes into contact with the electrodeshaving a small pitch. An inspection for determiningdefectiveness/nondefectiveness (particularly, the presence/absence of adisconnection) of such a board having patterns (conductive paths) with asmall pitch has often relied on visual observation or the like.

[0005] In recent years, the conductive patterns of a board (inspectiontarget board) have a higher density (smaller pitch) along with decreasesin size and weight of electronic devices. The decrease in pitch tends tocause disconnections in conductive patterns. A strong demand hastherefore arisen for board inspection meeting this tendency. Demands forimproving workability and reliability and decreasing the cost havebecome important.

[0006] In inspection for a board having patterns with a small pitch, inaddition to a problem posed by the difficulty in accurate positioning ofprobes on electrodes, another problem is posed by an increase in thenumber of measuring points. More specifically, In such a board, when thewiring density of conductive patterns increases (i.e., when the pitchbecomes small), the number of input and output points (the number ofmeasuring points) increases. Even if contact probing is possible, it istechnically difficult to maintain stable contact precision and contactproperties. In addition, as the test conditions are becoming stricterthan before, complicated, high-precision inspection jigs must beprepared, resulting in high cost.

[0007] Under these circumstances, several prior-art techniques based onnon-contact probing, i.e., the board inspection free from the problemposed by contact between probes and electrodes are known.

[0008] For example, British Patent No. GB2143954A has proposed atechnique for positioning a probe electrode at the end of a conductivepath to form capacitive coupling between the electrode and the end ofthe conductive path. An AC signal is applied between the electrode andthe one end of the conductive path, and a signal is detected at theother end of the conductive path through the above capacitive coupling.By this technique, a board can be inspected without bringing the probeinto contact with the conductive pattern.

[0009] Japanese Patent Laid-Open No. 6-34714 (U.S. Pat. No. 5,254,953)is deemed an improved proposal of the non-contact inspection methoddisclosed in GB2143954A described above.

[0010] Japanese Patent Laid-Open No. 5-264672 (U.S. Pat. No. 5,274,336)discloses a capacitive coupling probe (probe chip) used in an in-circuittest for a high-density circuit board.

[0011] In the above prior arts, the “non-contact” means coupling freefrom ohmic contact and is equivalently used as the “capacitive”. Thatis, a means for capacitive coupling is a capacitor.

[0012] The present inventor found that when the above prior-artinspection method and apparatus, however, were applied to a circuitboard such as a bare board prior to mounting circuit parts thereon, itwas difficult to highly accurately detect the presence/absence of adefect (e.g., a disconnection). That is, even if the prior-art techniqueis used to inspect a board in which the presence of a disconnection hasbeen confirmed, an inspection result representing the absence of adisconnection is obtained. The present inventor found the cause for thisas follows.

[0013]FIG. 2 is a block diagram of an inspection apparatus in U.S. Pat.No. 5,254,953. This prior-art technique is an apparatus serving as anin-circuit tester. This tester inspects to find whether a lead wire 111of an IC package 110 is normally connected to a lead wire 140 on acircuit board by soldering 200. That is, the tester inspects solderedportions, but does not inspects the pattern itself for any defects.

[0014] Referring to FIG. 2, an AC signal is supplied from an oscillator100 to the lead wire 140 between a probe electrode 120 and the lead wire111 through a capacitor layer formed by air layer and the IC package110. A shield 130 is arranged to prevent the probe electrode 120 frompicking up EMI (Electro-Magnetic Interference) from various devices (notshown) located above the probe electrode 120.

[0015] If soldering 200 is proper, the AC signal is detected by anelectrode 310 and measured by an inspection apparatus 300. Whethersoldering is defective or nondefective is determined by the magnitude ofthe signal detected by the electrode 310. Note that the capacitance ofthe capacitor layer formed by the air layer and the IC package 110between the probe electrode 120 and the lead wire 111 is as small asseveral femtofarad (fF), and the amplitude of the signal detected by theelectrode 310 is very small.

[0016] The present inventor found that when this probe electrode 120 wasapplied to a bare board 500, as shown in FIG. 3, the measurement of asignal by the electrode 310 upon intentionally forming a disconnection510 in a lead wire 520 on the board 500 had almost no difference in theamplitude of the detection signal from the measurement of a signal bythe electrode 310 through a lead wire 520 free from disconnections.

[0017] According to the findings of the present inventor, no differencewas found in detection signal between the cases in which thedisconnection 510 was present and it was absent because the signalapplied to the probe electrode 120 propagated in the electro-magneticfield formed in the air layer and was received by a lead wire portion520 a, and the signal on the lead wire portion 520 a was detected by theelectrode 310.

[0018] Although the inspection apparatus in FIG. 3 has the shield 130which is effective to protect the probe electrode 120 from the EMIsignal coming from above, the inspection apparatus is defenselessagainst radiant waves from various radiant sources located below theelectrode 120.

[0019] In inspecting a bare board, as shown in FIG. 3, the probeelectrode must particularly come closer to the bare board. In theinspection apparatus disclosed in U.S. Pat. No. 5,254,953 to inspect anin-circuit board which need not bring a probe electrode closer to theboard due to the presence of parts, the problem posed by the EMI signalfrom the board does not arise because the probe electrode is used faraway from the board.

SUMMARY OF THE INVENTION

[0020] It is an object of the present invention to provide a boarddetection probe and a board inspection method and apparatus, wherein ashield for preventing an EMI signal from acting on a pattern on a boardor from being emitted from the pattern in the board inspection apparatusfor inspecting the board by causing a probe to come close to the board,thereby realizing highly accurate inspection.

[0021] In order to achieve the above object, a board inspection probe(600, 700) for inspecting a pattern line on a circuit board for a defectin a non-contact manner comprises:

[0022] a main body;

[0023] an electrode (620) formed at a position near a board side of themain body and having a conductive electrode surface (620 h) forradiating an electrical signal toward a first pattern line (520) orreceiving an electrical signal radiated from the first pattern line; and

[0024] a shield (610) which is at least electrically grounded, wherein

[0025] the shield (610) has

[0026] a blank surface which does not shield a radiant wave to a secondpattern line (520 a) or a radiant wave from the second pattern line (520a) in a first region of the board which substantially corresponds to theelectrode surface of the electrode, and

[0027] a shield surface (610 a, 610 b, or 650) having an end portionextending near an end portion of the electrode surface without being inelectrical contact with the end portion of the electrode surface inorder to mainly shield a radiant wave to a third pattern line (520 b) ora radiant wave from the third pattern line (520 b) in a second regionexcept the first region on the board.

[0028] It is another object of the present invention to provide aninspection method and apparatus using the probe having the abovearrangement.

[0029] It is still another object of the present invention to provide aprobe in which the shield surface (610 a, 610 b) of the shieldhorizontally and vertically extends to partially cover a verticalsurface of the electrode.

[0030] It is still another object of the present invention to provide aprobe in which the shield surface (610 a, 610 b) vertically andhorizontally extends to entirely cover the vertical surface of theelectrode.

[0031] According to an aspect of the present invention, pattern lineshaving a pitch of several decade μm are formed on the board as a targetboard of a probe of the present invention.

[0032] According to another aspect of the present invention, the boardas a target board of the probe of the present invention is a bare boardprior to mounting circuit parts thereon, and the electrode surface hasan area substantially equal to that of the circuit parts in thehorizontal direction.

[0033] According to still another aspect of the present invention, theelectrode surface of the probe has a size of several cm² to several mm².

[0034] According to still another aspect of the present invention, theshield surface is divided into a first region (610 v-1) and a secondregion (610 v-2) in a direction perpendicular to the electrode surface.

[0035] It is still another object of the present invention to provide aprobe structure suitable for a probe using a low-profile electrode, inwhich

[0036] the shield comprises a two-dimensionally spread flat conductivemember (650), and

[0037] the member has an opening serving as the blank surface atsubstantially the center thereof, and

[0038] a conductive region extending in a direction parallel to theelectrode surface so as to surround the opening.

[0039] It is still another object of the present invention to provide aboard inspection method of applying an AC signal to the end portion of apattern line serving as an inspection target or detecting an inspectionsignal at the end portion of the pattern line, and at the same timegrounding the end portion of a pattern line except the target patternline.

[0040] According to an aspect of the inspection method of the presentinvention, the end portion of the target pattern line is sequentiallyswitched.

[0041] According to an aspect of the inspection apparatus of the presentinvention, the inspection apparatus further comprises means for moving aprobe in an arbitrary direction.

[0042] Other features and advantages of the present invention will beapparent from the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0043]FIG. 1 is a view showing pattern lines terminating with largepitches at its two terminals;

[0044]FIG. 2 is a diagram showing the arrangement of a board inspectionapparatus system using a conventional probe;

[0045]FIG. 3 is a view for explaining a state in which a probe used inthe inspection system in FIG. 2 picks up unwanted radiant waves;

[0046]FIG. 4 is a view showing the arrangement of a probe assemblyaccording to the first embodiment of the present invention;

[0047]FIG. 5 is a plan view showing the arrangement of a probe assemblysuitable for inspecting a board on which pattern lines extend in fourdirections, the probe assembly being an example of the probe assembly ofthe first embodiment (FIG. 4);

[0048]FIG. 6 is a perspective view showing the arrangement of a probeassembly in which a shield is divided into upper and lower regions, theprobe assembly being as another example of the probe assembly of thefirst embodiment (FIG. 4);

[0049]FIG. 7 is a view for explaining the arrangement of a probeassembly according to the second embodiment of the present invention;

[0050]FIG. 8 is a perspective view showing an example of the probeassembly of the second embodiment (FIG. 7);

[0051]FIG. 9 is a block diagram showing the arrangement of a boardinspection apparatus (first embodiment) using a probe assembly of thepresent invention;

[0052]FIG. 10 is block diagram showing the arrangement of a boardinspection apparatus (second embodiment) using a probe assembly of thepresent invention; and

[0053]FIG. 11 illustrates how teaching points are arranged in aninspection system according to a modified embodiment in which one probeassembly is moved to the points.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] Two probes to which the present invention is applied, and oneinspection apparatus using these probes will be described with referenceto the accompanying drawings.

[0055] <Probe Assembly> . . . First Embodiment

[0056]FIG. 4 is a view for explaining the principle of the arrangementof a probe assembly 600 according to the first embodiment to which thepresent invention is applied.

[0057] The probe assembly 600 includes an electrode 620 and a shield610. Reference numeral 500 denotes a board serving as an inspectiontarget.

[0058] Pattern lines 520 and 530 are formed on the board 500. Adisconnection 510 is present in the pattern line 520. The pattern line520 is separated into pattern line portions 520 a and 520 b due to thepresence of this disconnection. FIG. 4 shows a state in which the probeassembly 600 according to the first embodiment is positioned above thepattern line portion 520 b by a positioning device (not shown). Anelectrode 310 is connected to one end of the pattern line portion 520 a.

[0059] When an AC inspection signal is applied to the electrode 310, anelectric field or electro-magnetic field is formed along the patternline 520. In other words, weak radiant waves are generated from allportions of the pattern line 520 and they are apt to reach the electrode620. Since the disconnection 510 is present on the board 500, thepattern line portion 520 b generates no radiant waves, but the patternline portion 520 a generates radiant waves. If the pattern line 530 iscapacitively coupled to or in ohmic contact with the pattern line 520,the pattern line 530 also generates radiant waves.

[0060] Since the pattern line 520 serving as the inspection target hasthe disconnection 510, the electrode 620 should not receive any radiantwave. The shield 610 prevents unwanted radiant waves (radiant waves fromthe pattern line portion 520 a and the pattern line 530 in FIG. 4) fromreaching the electrode 620. The pattern line portion 520 b generates noradiant waves, and the electrode 620 receives no radiant waves.Therefore, the amplitude of the detection signal is zero or has a verylow level.

[0061] If no disconnection 510 is present, the radiant waves from thepattern line portion 520 b are received by the electrode 620 while theradiant waves from the pattern line portion 520 b are shielded. When theelectrode 620 is connected to an amplifier (not shown), an amplifiedsignal can be monitored to determine the presence/absence of adisconnection.

[0062] The shield 510 must covers the electrode 620 so that theelectrode 620 may not receive any unwanted radiant waves. In FIG. 4,shields 610 a and 610 b cover vertical surfaces 620 a and 620 b of theflat electrode 620 so that these vertical surfaces 620 a and 620 b todetect radiant waves from the pattern line portion 520 a and the patternline 530.

[0063] Pattern lines (pitch: several decade μm) are formed at a veryhigh density on a board to be inspected by this inspection probeassembly. The amplitude of a signal to be applied to the electrode 310is small, and its frequency is also low (about 10 kHz). For this reason,to detect a signal having a large amplitude by the probe, the probeassembly 600 must come very close to the board surface.

[0064] When the probe assembly 600 comes very close to the board,radiant waves from the pattern line portion 520 a and the pattern line530 will not round about to be received by a horizontal surface 620 h ofthe electrode 620.

[0065] When the probe assembly 600 need not come very close to the board(e.g., when pattern lines have a large pitch, or the frequency orvoltage of an inspection signal is high), the horizontal surface 620 hof the electrode of the probe assembly 600 is separated from thesubstrate surface. Therefore, the horizontal surface 620 h of theelectrode 620 may receive the radiant waves from the pattern lineportion 520 a and the pattern line 530. In this case, the shields 610 aand 610 b must be further extended downward.

[0066] The shield 610 need not entirely cover the vertical surfaces ofthe electrode 620 because a vertical surface in a given direction maynot have any pattern line portion in this direction. As the layout ofpattern lines on a board serving as an inspection target is known, avertical surface in an unnecessary direction need not be formed on theshield 610. That is, the shield preferably has directivity, as needed.

[0067]FIG. 5 is a plan view of an example of the probe assembly 600 forinspecting a board having pattern lines extending in four directionswhen viewed from the top. In this example, vertical surfaces 610 v of ashield are formed to surround the horizontal surface 620 h of theelectrode 620. FIG. 6 is a perspective view of the probe assembly 600 inFIG. 5.

[0068] A central metal conductor 630 forms an electrode. The effectivesurface of this electrode is formed on the lower surface of the metalconductor 630. Reference numeral 635 in FIG. 6 denotes an insulatinglayer for insulating the vertical surfaces 610 v of the shield from themetal conductor 630 serving as an electrode. The shield having thevertical walls 610 v is made of conductive metal. In the example shownin FIG. 6, the shield covers the vertical wall surfaces of the metalconductor 630 with inner surfaces. The shield is divided by a boundary610 into an upper region made of a metal net and a lower region made ofa copper plate. The upper region shields the electrode from radiantsources (e.g., power supply lines of the inspection apparatus andprobing wiring lines) of various waves outside the board.

[0069] The size of the electrode surface of the probe assembly isdetermined in accordance with the size of parts to be mounted on thebare boards serving as a measurement target, i.e., the degree of spreadat the end portions of pattern lines on the board. For example, thesizes of parts generally range from several mm to several cm, and thesizes of electrode portions range from several mm to several cm,accordingly.

[0070] <Probe Assembly> . . . Second Embodiment

[0071]FIG. 7 shows the structure of a probe assembly 700 according tothe second embodiment. An electrode 620 itself of the probe assembly ofthe second embodiment is identical to the electrode 620 of the probeassembly of the first embodiment. The probe assembly 700 is differentfrom the probe assembly of the first embodiment in the shield structure.

[0072] Since the electrode 620 receives radiant waves, the height of theelectrode need not be large. The length of a vertical surface 620 v inthe direction of height can be small. The vertical surface 620 v mayreceive unnecessary radiant waves although the vertical surface 620 islow (its length is small). For this reason, the probe assembly 700 ofthe second embodiment has a flat shield 650 extending in the horizontaldirection.

[0073]FIG. 8 is a perspective view of the shield 650. An opening isformed at the center of the shield 650. The electrode 630 is stored inthe opening of the shield 650. A gap 660 is formed between the electrode620 and the shield 650 and is preferably filled with an insulatingmaterial. The material connects and fixes the electrode 620 to theshield 650. The shield 650 moves together with the electrode 620 uponmovement of the electrode 620.

[0074] <Inspection Apparatus System> . . . First Embodiment

[0075]FIG. 9 is a block diagram showing the arrangement of a boardinspection apparatus system to which a probe assembly of the presentinvention is applied. Each of the probe assemblies of the above twoembodiments is applicable to the system shown in FIG. 9.

[0076] This inspection system is suitable for an inspection of a boardhaving a larger number of pattern lines such that the terminals (theelectrode 310 in FIG. 4) of the pattern lines as an inspection target onone side have a relatively large pitch, and the terminals of the patternlines on the side of mounted parts such as IC packages have a very smallpitch.

[0077] Referring to FIG. 9, reference numeral 600 denotes the probeassembly of the first or second embodiment. This probe assembly 600 isconnected to a jig plate 900 which is capable of accommodating aplurality of probe assemblies. A personal computer 800 controls the jigplate 900 to move downward to fit the probe assemblies 600 closer to aboard 700, and to move upward to separate from the board 700 when ameasurement test is terminated.

[0078] A pattern line group constituted by a large-pitch pattern lineportion 750 and a small-pitch pattern line portion 760 is formed on theboard 700 as an inspection target. The board 700 is entirely grounded bya ground plate 680 disposed under the board 700.

[0079] The terminals of the large-pitch pattern line portion 750 areconnected to the probes of a probe group 706, respectively. The leadwires from the probe group 706 are connected to a switch box 705.

[0080] Referring to FIG. 9, reference numeral 701 denotes an oscillatorfor generating a DC inspection signal; 702, a DC power supply forgenerating a DC signal; and 703, a power supply relay for switchingbetween the AC signal from the oscillator 701 and the DC signal from thepower supply 702. A switch 704 is a two-contact switch, one contact(contact b) of which is grounded.

[0081] The switch box 705 has switch elements whose number is largerthan or equal to that of the contact probes of the contact group 706.Each switch element has two contacts. When each switch element isconnected to the a side, the signal from the relay 703 is supplied tothe corresponding contact probe of the probe group 706. When each switchelement is connected to the b side, the potential from the switch 704 issupplied to the corresponding contact probe of the probe group 706.

[0082] The signal detected by the probe assembly 600 is supplied to awaveform processor 710 and subjected to filtering in a filter (BPF) 711.The output from the filter 711 is amplified by an amplifier 712. Theamplified signal is converted into a digital signal by an A/D converter713. The digital signal is fetched into the personal computer 800.

[0083] Note that the conductive pattern of the illustrated inspectiontarget board 700 has 5-channel conductive paths for illustrativeconvenience. However, the number of channels is not limited to aspecific one.

[0084] Short-Circuiting Test

[0085] A short-circuiting inspection for the conductive patterns of thepattern line portion 760 will be described first.

[0086] The personal computer 800 controls the relay 703, the switch 705,and the switch box 705 as follows.

[0087] That is, the switch 704 is connected to the a side, i.e., theoutput from the switch 704 is connected to the A/D converter.

[0088] Of the plurality of switch elements of the switch box 705, onlythe switch elements connected to the probes of the probe group 706connected to the pattern lines serving as the inspection targets areconnected to the terminal b sides, and the remaining switches in theswitch box 705 are connected to the terminal a sides.

[0089] At the same time, the personal computer 800 controls to connectthe relay 703 to the terminal b side. A DC voltage is applied from theDC power supply 702 to the inspection target pattern lines.

[0090] If short-circuiting has occurred in an arbitrary pattern line onthe board 700, the DC voltage applied to the inspection target patternline (i.e., a pattern line connected to the uppermost probe in FIG. 9)is returned through the short-circuited pattern line and input to an A/Dconverter 714 through the contact a side of the switch 704. If noshort-circuiting is present, the potential detected on the terminal aside of the switch 704 must be low. The personal computer 800 monitorsthe output signal from the A/D converter 714 to determine whethershort-circuiting has occurred in the inspection target pattern lines.

[0091] Note that the target pattern lines in the short-circuiting testcan be switched by switching the switches in the switch box 705.

[0092] Disconnection Test

[0093] A disconnection inspection for a conductive pattern will bedescribed below.

[0094] To perform a disconnection test, the relay 703, the switch 704,and the switch box 705 will be controlled as follows. More specifically,the switch 704 is connected to the terminal b side and grounded. Of theplurality of switch elements in the switch box 705, only the switchelements connected to the probes of the probe group 706 connected to theinspection target pattern lines are connected to the b sides, and theremaining switches in the switch box 705 are connected to the a sides.At the same time, the personal computer 800 controls to connect therelay 703 to the terminal a side. Therefore, an AC signal is appliedfrom the oscillator 701 to the inspection target pattern lines.

[0095] Pattern lines except the inspection target pattern lines aregrounded to suppress generation of unnecessary radiant waves from thepattern lines except the inspection target pattern lines.

[0096] The AC signal applied to the inspection target pattern lines isreceived as radiant waves by the electrode of the probe assembly 600.The received radiant waves are filtered by the BPF 711 as an electricalsignal. The electrical signal is amplified and converted into a digitalsignal.

[0097] The personal computer 800 compares the input signal from the A/Dconverter 713 with a predetermined threshold value to determine whethera disconnection is present. More specifically, if a disconnection ispresent in one of the inspection target pattern lines, the voltage levelof the signal from the A/D converter 713 is much lower than thereference level. Therefore, the presence/absence of a disconnection canbe discriminated in accordance with this level difference.

[0098] <Inspection Apparatus> . . . Second Embodiment

[0099] The inspection apparatus of the first embodiment applies an ACinspection signal to the terminals of the large-pitch pattern lineportion. An inspection system of the second embodiment applies an ACinspection signal from the electrode of a probe assembly 600 to asmall-pitch pattern line portion.

[0100] The constituent elements of the inspection apparatus of the firstembodiment can be applied to the inspection apparatus of the secondembodiment. The same reference numerals as in the first embodiment ofFIG. 9 denote the same parts in FIG. 10.

[0101] Short-Circuiting Test

[0102] A short-circuiting inspection for conductive patterns of apattern line portion 760 will be described first.

[0103] Referring to FIG. 10, a personal computer 800 controls a relay703, a switch 704, and a switch box 705 as follows.

[0104] That is, the switch 704 is connected to the a side, i.e., theoutput from the switch 704 is connected to the A/D converter.

[0105] Of the plurality of switch elements of the switch box 705, onlythe switch elements connected to the probes of a probe group 706connected to the pattern lines serving as the inspection targets areconnected to the terminal b sides, and the remaining switches in theswitch box 705 are connected to the terminal a sides. At the same time,the personal computer 800 controls to connect the relay 703 to theterminal b side. A DC voltage is applied from a DC power supply 702 tothe inspection target pattern lines.

[0106] If short-circuiting has occurred in an arbitrary pattern line ona board 700, the DC voltage applied to the inspection target patternline (i.e., a pattern line connected to the uppermost probe in FIG. 10)is returned through the short-circuited pattern line and input to an A/Dconverter 714 through the contact a side of the switch 704. If noshort-circuiting is present, the potential detected on the terminal aside of the switch 704 must be low. The personal computer 800 monitorsthe output signal from the A/D converter 714 to determine whethershort-circuiting has occurred in the inspection target pattern lines.

[0107] Note that the target pattern lines in the short-circuiting testcan be switched by switching the switches in the switch box 705 as inthe inspection apparatus of the first embodiment.

[0108] Disconnection Test

[0109] A disconnection inspection for a conductive pattern in theapparatus of the second embodiment will be described below.

[0110] To perform a disconnection test, the relay 703, the switch 704,and the switch box 705 will be controlled as follows with referring toFIG. 10. More specifically, the switch 704 is connected to the terminalb side and grounded. Of the plurality of switch elements in the switchbox 705, only the switch elements connected to the probes of the probegroup 706 connected to the inspection target pattern lines are connectedto the b sides, and the remaining switches in the switch box 705 areconnected to the a sides.

[0111] Pattern lines except the inspection target pattern lines aregrounded to suppress generation of unnecessary radiant waves from thepattern lines except the inspection target pattern lines.

[0112] At the same time, the personal computer 800 controls to connectthe relay 703 to the terminal a side, so that the relay 703 is connectedto a BPF 711.

[0113] The personal computer 800 then drives an oscillator 701. The ACsignal from the oscillator 701 is applied to the inspection targetpattern lines through the probe assembly 600.

[0114] The radiant waves received by the inspection target pattern linesappear on the probe group 706 and filtered by the BPF 711 as anelectrical signal. The electrical signal is amplified and converted intoa digital signal.

[0115] The personal computer 800 compares the input signal from the A/Dconverter 713 with a predetermined threshold value to determine whethera disconnection is present. More specifically, if a disconnection ispresent in one of the inspection target pattern lines, the voltage levelof the signal from the A/D converter 713 is much lower than thereference level. Therefore, the presence/absence of a disconnection canbe discriminated in accordance with this level difference.

[0116] <Modifications>

[0117] Referring to FIG. 9, the jig plate 900 may be substituted by apositioning stage 900 capable of positioning the probe assembly 600three-dimensionally (X, Y, and Z directions). The personal computer 800controls the stage 900 to move the probe assembly 600 to an arbitraryposition on a board 700. As shown in FIG. 11, the target movingpositions (indicated by open circles in FIG. 11) are in advance byteaching, and teaching point data for each board are stored in a memory(not shown) in the personal computer 800.

[0118] θ axis is preferably added to the X, Y, and Z directions in apositioning stage 900 in order to adjust directivity.

[0119] <Advantages of Embodiments>

[0120] As has been described above, since a probe according to thepresent invention can shield radiant waves which are emitted from allsources located below the probe electrode and interfere with inspection,board inspection using this probe can be performed with a high accuracy.

[0121] As many apparently widely different embodiments of the presentinvention can be made without departing from the spirit and scopethereof, it is to be understood that the invention is not limited to thespecific embodiments thereof except as defined in the appended claims.

What is claimed is:
 1. A board inspection probe (600, 700) forinspecting a pattern line on a circuit board for a defect in anon-contact manner, comprising: a main body; an electrode (620) formedat a position near a board side of said main body and having aconductive electrode surface (620 h) for radiating an electrical signaltoward a first pattern line (520) or receiving an electrical signalradiated from said first pattern line; and a shield (610) which is atleast electrically grounded, wherein said shield (610) has a blanksurface which does not shield a radiant wave to a second pattern line(520 a) or a radiant wave from said second pattern line (520 a) in afirst region of said board, said first region substantiallycorresponding to said electrode surface of said electrode, and a shieldsurface (610 a, 610 b, or 650) having an end portion extending near anend portion of said electrode surface without being in electricalcontact with said end portion of said electrode surface in order tomainly shield a radiant wave to a third pattern line (520 b) or aradiant wave from said third pattern line (520 b) in a second regionexcept the first region on said board.
 2. The probe according to claim 1, wherein said main body has vertical and horizontal surfacessubstantially perpendicular and parallel to a surface of said board,said electrode surface (620 h) is formed substantially parallel to saidhorizontal surface, and said shield surface (610 a, 610 b) of saidshield vertically and horizontally extends to cover at least part ofsaid vertical surface of said main body on said vertical surface.
 3. Theprobe according to claim 2 , wherein said shield surface (610 a, 610 b)vertically and horizontally extends to entirely cover said verticalsurface of said main body.
 4. The probe according to claim 1 , whereinpattern lines having a pitch of several decade μm are formed on saidboard.
 5. The probe according to claim 1 , wherein said board is a bareboard prior to mounting circuit parts thereon, and said electrodesurface has an area substantially equal to that of said circuit parts ina planar direction.
 6. The probe according to claim 1 , wherein saidelectrode surface has a size of several mm² to several cm².
 7. The probeaccording to claim 1 , wherein said shield surface is divided into afirst region (610 v-1) and a second region (610 v-2) in a directionperpendicular to said electrode surface, said shield surface within thefirst region shields radiation from or to said pattern lines on saidboard, and said shield surface within the second region shieldselectro-magnetic interference coming from above said board.
 8. The probeaccording to claim 1 , wherein said shield comprises a two-dimensionallyspread flat conductive member (650), and wherein said member has anopening as said blank surface at a substantially center thereof, and hasa conductive region extending in a direction parallel to said electrodesurface, and surrounding the opening.
 9. An inspection method forinspecting a board using said probe defined in claim 1 .
 10. The methodaccording to claim 9 , further comprising using as an inspection targeta board on which pattern lines having a pitch of several decade μm areformed.
 11. The method according to claim 9 , further comprisingbringing said probe into substantial contact with said board while saidprobe is electrically insulated from said board.
 12. The methodaccording to claim 9 , wherein said board is a bare board prior tomounting circuit parts thereon, and said electrode surface has an areasubstantially equal to that of said circuit parts in a planar direction.13. The method according to claim 9 , further comprising applying an ACsignal to an end portion of an inspection target pattern line on saidboard and detecting an inspection signal at said electrode.
 14. Themethod according to claim 9 , further comprising applying an AC signalto said electrode and detecting an inspection signal at an end portionof an inspection target pattern line on said board.
 15. The methodaccording to claim 9 , further comprising applying an AC signal to anend portion of an inspection target pattern line on said board ordetecting an inspection signal at said end portion of the pattern line,and grounding an end portion of a pattern line except the inspectiontarget pattern line.
 16. The method according to claim 9 , furthercomprising sequentially switching the end portions of the inspectiontarget pattern lines.
 17. A board inspection apparatus using saidinspection method of claim 9 .
 18. The apparatus according to claim 17 ,further comprising means for moving said probe in an arbitrarydirection.
 19. A board inspection apparatus using said inspection methodof claim 10 .
 20. A board inspection apparatus using said inspectionmethod of claim 11 .
 21. A board inspection apparatus using saidinspection method of claim 12 .
 22. A board inspection apparatus usingsaid inspection method of claim 13 .
 23. A board inspection apparatususing said inspection method of claim 14 .
 24. A board inspectionapparatus using said inspection method of claim 15 .
 25. A boardinspection apparatus using said inspection method of claim 16 .